This invention relates to a seat support mechanism for a tiltable chair of the type commonly found in offices. It is known in the art to tiltably support a seat of a chair utilizing a torsion bar spring mechanism. A torsion bar extends transversely of the seat having one of its ends nonrotatably secured relative to the member to be tilted and the other end nonrotatably secured to a support member whereby tilting of said member about the longitudinal axis of the torsion bar is restrained by twisting of said bar. See, for example, U.S. Pat. Nos. 2,991,125, 3,131,904, 3,480,249, 3,592,433, and 4,295,626.
It is also known that instead of utilizing a single torsion bar, a pair of torsion bars can be used to decrease the overall width and provide a more compact construction, one end of one torsion bar being nonrotatably connected to a member supporting the frame, both torsion bars being interconnected to twist under reciprocal influence to act as a single torsion bar. See, for example, U.S. Pat. No. 3,868,144.
All of these prior art patents, however, have focused on an arrangement which resists only the rearward tilt of the seat of a chair when the occupant leans backward. None have provided a mechanism with separate axes and separate controls for front and rear tilt.